It’s Icelandic so I’m not 100% sure. Icelandic is pretty different and much more like Norse. Their names are also pretty different. I used a pronounciation guide to help me but it could still be a bit wrong.
The u in Mun is like the o sound is sew, row, low, etc, but only the last part when your mouth is less open. It can be a difficult sound for English speakers to get right. The vowel in knörr is much like the u in sun, but a bit less like a u and more like an a. Can also be difficult for English speakers. The rr is like a normal r except sharper. Even I probably can’t pronounce it properly. Munknörr is obviously not an icelandic name. I don’t know what it means. I’m guessing “mun” is the stressed part of the word.
& is “og”. O is like the vowel in saw, but not as long. G is like a g in hag, bag, etc. They say this g differently, with more air.
The sig in sigur is lik cig in cigarette. Same thing with the g. The u here is like the o in lose, but slightly shorter. The r is the sharp r again. Bo in boði is like ba in ball but again a bit shorter, ð is like th in thing, and i is like the ee in see.
The g in grétar is like a regular g (bag, etc). This time without any extra airy sound to it. R is the sharp r. É is pretty much like “yeah”, more specifically like the ye in yes. Tar is like tar (the word), but with the icelandic sharp r. The vowel in sson (the first s is just the possessive s of his father’s name but they are pronounced like a regular s) is again like saw, but shorter.
The first syllable is probably stressed in each name/word.
If you listen to some Icelandic you might get an idea of how it would sound. But Icelandic is difficult.
Edit: if “munknörr” is two words, mun+knörr, the u would be like in sigur instead. But Norse is a dead language so it’s probably not very important.